We have an established and very healthy amelanchier. This last week or so we have noticed large numbers of leaves changing to autumn colour and then shedding them . Is this usual and are there any obvious reasons?

Mine has had a lot of smaller branches snap off, I thought it was my son and I noticed that the leaves looked autumnal, I put that down to having the branches fall off and it upsetting the tree. It has been very dry the past month, perhaps they are suffering from that or the wind?